The objective of this project is to determine the nature of the host response to allogeneic tissues placed in the anterior chamber of the eye. It is clear that the anterior chamber of the eye is a privileged site despite the fact that the host can recognize the presence of the foreign tissue and mount an immune response but rejection is delayed. That the host can mount an immune response to skin implants placed in the anterior chamber of the eye is evident by an early cellular infiltration, active enhancement of subsequent orthotopic skin grafts and the production of migration inhibition factors (MIF) several weeks before rejection of the implants is complete. Serum blocking factors have been discovered in the serum of implant-bearing rats which may help prevent the rapid destruction of the implant by the host lymphocyte. Studies will be performed to determine if active enhancement and blocking factor production occur when tissues other than skin are placed in the anterior chamber. Studies will be continued using the Brown Norway to Lewis rat skin implant system which is a proven model for studying the host's immune response to antigenic stimulation via the anterior chamber of the eye. The cell mediated response of the host will be measured by the MIF, mixed lymphocyte, mitogen stimulation and cell cytotoxicity reactions. The humoral response will be assayed by the agglutination and complement mediated serum cytotoxicity reactions.